1. Field of the Invention
The present invention relates to an improvement in a medical apparatus used during the performance of eye surgery. In particular, the present invention is directed towards an improved cutting blade assembly to be used in conjunction with an automatic surgical device for cutting the cornea of a patient""s eye. The present invention is further directed towards a control assembly for use with an automatic surgical device which is capable of shutting off power supplied to the device when problems are encountered during the surgical cutting of the cornea.
2. Description of the Related Art
Until about twenty years ago, refractive errors of light passing through the eye could only be treated with eyeglasses or contact lens, both of which have well known disadvantages for the user. Consequently, in the last several years, research has been directed to surgical operations to change the refractive condition of the eye, i.e., either to flatten or increase the curvature of a patient""s eye depending upon his or her condition. The desired result of such surgical operations is that light rays passing through the cornea will be refracted to converge properly and directly onto the retina so as to allow a patient to clearly see close or distant images.
Automated Lamellar Keratectomy (ALK) is one surgical technique developed wherein the eye is first numbed by a drop of anesthetic, and then a suction ring is placed on the eye to carefully position the cornea (termed xe2x80x9ccentrationxe2x80x9d in the art) for being cut by a very fine microsurgical instrument known as a microkeratome. The microkeratome is generally a blade carrying device that must be manually pushed or mechanically driven in a cutting path across the suction ring simultaneous with the motorized movement of the cutting element, which movement is transverse to the direction of the cutting path. For treating myopia pursuant to ALK procedures, the microkeratome is typically used to first cut into the cornea so as to raise and separate a thin layer of the anterior cornea of between 100-200 microns in depth and about 7 millimeters in diameter. Next, the microkeratome is then used to make a second pass over the cornea to resect or remove a smaller part of the cornea, generally about 4 to 6 millimeters in diameter, which is then discarded. The anterior corneal cap which was cut away with the first pass of the microkeratome is then put back into its original position, without suturing, for healing to occur. The desired result of this procedure is that the cornea will have a new curvature because of the resected tissue, which provides a new refracting surface to correct the patient""s original myopic condition. To correct hyperopia under ALK however, the microkeratome is typically used to make a single deep pass over the cornea. The cut layers are put back into their original position, without any removal of any other tissue. Because of the depth of the cut, the intraocular pressure within the eye causes a steepening of the cornea to again, provide a new refracting surface which hopefully will correct the patient""s original hyperopic condition.
Another more recent advance in surgical procedures to correct refractive errors of the eye involves the introduction of laser procedures. One such procedure, known as Laser Intrastromal Keratomileusis, (LASIK), is currently considered optimal because it allows sculpting of the cornea by a laser, without damaging adjacent tissues. Moreover, with the aid of computers, the laser can be programmed by a surgeon to precisely control the amount of tissue removed, and significantly, to permit more options for the reshaping of the cornea. Under LASIK procedures, the eye is still typically positioned within a suction ring and a microkeratome is typically used to cut into the cornea so as to raise a thin layer of the cornea.
In recent years, it has been learned that regardless of whether ALK or LASIK surgery is performed, the microkeratome which cuts the cornea should not create a corneal cap nor separate the cut corneal tissues completely from the rest of the cornea. The reasons are primarily two-fold: first, the possibility exists that when the corneal cap is put back in place on the cornea, it will not be aligned properly with the remaining corneal tissues, which has several drawbacks for the patient, and second, the possibility exists that the corneal cap will become lost during the surgery, and if that occurs, the consequences for the patient are catastrophic. In great part to overcome these problems, among others, the inventor of the invention described in the present application created and developed an improved surgical device for cutting the cornea which automatically and reliably leaves a portion of the raised and separated corneal tissues connected or xe2x80x9chingedxe2x80x9d to the eye, thereby forming a raised layer of corneal tissue hinged to the eye, known as a corneal flap F, illustrated in FIG. 1.
Significantly, it has been determined that the corneal flap should have a depth of no less than 130 microns and no more than 160 microns to yield optimal results. It should be borne in mind that achieving this result during surgery requires an extremely precise instrument as one micron is a unit of length equal to one thousandth of a millimeter. Further, it is desirable, if not imperative, for the microkeratome to cut across the cornea in a manner that will very finely and smoothly cut the corneal tissues. In this regard, there is a need in the art for improvement in that when the smoothness of a cut made to the cornea by known microkeratome devices is closely examined under a microscope, the cut, corneal tissue edges are seen to be a bit irregular, if not slightly jagged. It would be ideal if a microkeratome device were able to cut across the cornea, not only so as to cut and raise the microscopicly thin layer of corneal tissue currently considered optimal, but to do so in a manner which results in a noticeably improved cut to the cornea, namely, by yielding very fine, smooth and almost undetectable cut corneal tissue edges.
In addition, there is room for known microkeratome devices to be improved with regard to the assembly required prior to performing surgery on a patient""s eye, as well as with regard to the disassembly, sterilization and cleaning of the device, or parts thereof, following surgery. Specifically, microkeratome devices, and particularly, the cutting blade housed therein, which penetrates into and cuts the cornea must be in a proper sanitary and sterilized state until generally about the moment when surgery on the eye is to begin. Known microkeratome devices, however, have required that the housing for the cutting blade be manipulated so as to create access to an interior thereof and permit the placement of the cutting blade therein, which itself must typically be handled as well, after which, the housing must again be manipulated so as to close off the access means, all of which has hopefully resulted in the cutting blade being properly in place. This excessive manipulation required of known microkeratome devices is not conducive, however, to maintaining the proper sanitary and sterilized state required for surgery. Moreover, in manipulating the access means of certain known microkeratome devices, some surgeons have unintentionally caused the cutting blade to become dislodged, or worse, have even bent the cutting blade, thereby requiring the assembly process to start over again. Further, the mechanisms within known microkeratome devices for holding the cutting blade have been designed for repeated use. This factor tends to only exacerbate the problems encountered in the art in that these known blade holding mechanisms should also be removed from the microkeratome device following a surgery in order to be properly cleaned and/or sterilized for subsequent use. The assembly and disassembly of these mechanisms are not only tedious and time consuming, but are fraught with the difficulties of maintaining sterilization and ensuring proper re-assembly.
Consequently, there is a need in the art for an improved microkeratome device for cutting the cornea of a patient""s eye which can easily receive and which facilitates the proper positioning of a cutting blade therein, without excessive manipulation. There is also a need for an improved cutting blade assembly that facilitates easy insertion within a microkeratome device, with little danger of becoming bent, while simultaneously offering the user the knowledge that it is securely and properly in place. Any such improved cutting blade assembly should similarly be quickly and easily removed from the microkeratome device, and will preferably be disposable. It would be ideal if any such improved cutting blade assembly could be readily packaged in containers that permit sterilization prior to shipping, and which remain sterilized during shipping, and further, which could be easily removed from the sterile packaging for insertion into the microkeratome while maintaining sterility. In this regard, any such improved cutting blade assembly would ideally include an instrument which facilitates the removal of the assembly from a sterile container and the insertion thereof into the microkeratome, while maintaining sterility.
Known microkeratome devices are thought to have other, fairly significant deficiencies as well. For example, when a surgery on a patient""s eye is underway, at times the suction or vacuum provided to temporarily attach the positioning ring to the cornea is either broken or interrupted. Given the precision cutting which is needed for such surgeries, however, it is highly undesirable, for the eye to continue to be cut during such situations. To date, known microkeratome devices continue cutting in such situations. Thus, it would be highly beneficial to provide an improved microkeratome device with a control assembly that could detect problems encountered during the surgical cutting of the cornea and that will shut off power supplied to the device when problems are detected so as to stop the cutting of the cornea by the microkeratome. Moreover, if surgery on a patient""s eye is proceeding well, but there is sudden power loss, any such control assembly should enable the microkeratome device to continue functioning during the rather short duration of the operation, without interruption, both in terms of continuing to ensure a power supply to the device and a supply of vacuum to the positioning ring.
The present invention is designed to satisfy the needs which remain in the art of microkeratome devices used to cut the cornea of a patient""s eye. In this regard, the present invention is directed towards an improved microkeratome which is able to cut and raise a microscopicly thin layer of corneal tissue in a manner that results in very fine, smooth and almost undetectable cut corneal tissue edges. In addition, the present invention is directed towards an improved microkeratome cutting blade assembly that permits quick and easy installation and removal from the microkeratome housing, without excessive manipulation. The present invention is further directed towards a control assembly for a microkeratome device that is capable of detecting problems encountered during the surgical cutting of the cornea and either shutting off power supplied to the device, if appropriate, or ensuring that power and/or a vacuum continue to be supplied to the device, if appropriate.
The cutting blade assembly of the present invention is seen to comprise an improved cutting blade and blade holder. The cutting blade comprises a front portion that includes a sharp, forward cutting edge, a rear, trailing portion having a rear edge, and a pair of side edges that extend and taper between the front and rear trailing portions. The cutting blade further includes at least one aperture formed therein, and preferably, a pair of apertures disposed in the rear, trailing portion in substantially aligned relation with one another. Preferably, the cutting blade is substantially flat and made of stainless steel, with the front portion of the cutting blade having an overall dimension which is larger than the rear trailing portion. The blade holder of the improved cutting blade assembly is formed so that an underside thereof is secured to the cutting blade at the at least one aperture on the cutting blade, and so that a top side of the blade holder includes means for being operably driven by the drive means of the microkeratome device, which may comprise a recess formed within the blade holder. In the preferred embodiment, the blade holder will be molded of a plastic material and will be press fit during manufacture into the at least one aperture on the cutting blade so as to provide an integrally formed cutting blade assembly. In a most preferred embodiment, the cutting blade assembly of the present invention will additionally comprise a tool which facilitates the removal of the cutting blade and blade holder from a sterile packing container and the insertion thereof in a microkeratome device, while maintaining sterility.
A primary object of the present invention is to provide an improved microkeratome and cutting blade assembly that markedly improves the cutting of the cornea, namely, one that is able to cut and raise a microscopicly thin layer of corneal tissue in a manner that results in very fine, smooth and almost undetectable cut corneal tissue edges, which can then be easily and more precisely aligned back into an original position on the cornea following the reshaping of the cornea.
Another primary object of the present invention is to provide a microkeratome device with improved access means for ensuring that either or both a cutting blade and blade holder can be easily and quickly installed for surgical use on a patient, while at the same time, facilitating cleaning of the microkeratome and one or more of its internal mechanisms.
It is a further important object of the present invention to provide a cutting blade assembly which is easily and quickly installed within a microkeratome device in preparation for surgical use on a patient, without excessive handling so as to maintain the sanitary condition of the assembly and device, and further which quickly offers confirmation that the assembly is securely and properly in place within the microkeratome.
It is also an object of the present invention is to provide an improved cutting blade and blade holder which is integrally formed and consequently, which is easy to remove from a microkeratome device, and ideally, which is disposable.
Yet another object of the present invention is to provide a cutting blade assembly which is readily packaged in containers that permit sterilization prior to and which remain sterilized during shipping, and further, which is easily removed from the sterile packaging for insertion into the microkeratome while simultaneously maintaining sterility.
A further object of the present invention is to provide a cutting blade assembly which can be used with either presently known microkeratome devices or with those that may be developed in the future.
It is a further object of the present invention is to provide an improved automated microkeratome device which is not only readily usable on either a patient""s left or right eye, but which readily informs a surgeon as to which eye the device is assembled for use on.
Yet another important object of the present invention is to provide an improved microkeratome device having a control assembly which will not allow the cutting of the cornea to continue during a surgery when the vacuum seal between the positioning ring and the eye becomes compromised and/or is broken.
Still another important object of the present invention is to provide a control assembly for a microkeratome device that is capable of detecting problems encountered during the surgical cutting of the cornea and which has back up capabilities to ensure that power and/or a vacuum continue to be supplied to the device.
A feature of the present invention is that it provides a control assembly for a microkeratome device that is internally electrically isolated between the high voltage and low voltage sides, while still permitting necessary checks and interaction between the components on both sides.
Another feature of the present invention is that it provides a control assembly for a microkeratome device that will not permit a motor to burn out if substantial resistance is encountered by the device as it cuts the cornea during an operation.
These and other objects, features and advantages of the present invention will be more readily understood upon consideration of the accompanying drawings as well as the detailed description of a preferred embodiment for the invention, which is set forth below.